Editing MPEG-1 Audio Layer II

{{short description|Lossy audio compression format}}
{{more footnotes|date=December 2016}}
{{Distinguish|MPEG-2}}{{Infobox file format
| name          = MPEG-1 or MPEG-2 Audio Layer II
| icon          = 
| logo          = 
| caption       = 
| extension     = .mp2, .mpa, .m2a, .mp2a
| mime          = audio/mpeg,{{ref RFC|3003}} audio/MPA{{ref RFC|3555}}
| type code     = 
| uniform type  = 
| magic         = 
| owner         = [[Philips]] and others
| released      = {{Start date and age|1991|12|06|df=yes}}<ref name="11172-draft-cite">{{Cite book |vauthors=Patel K, Smith BC, Rowe LA |title=Proceedings of the first ACM international conference on Multimedia - MULTIMEDIA '93 |chapter=Performance of a software MPEG video decoder |date=1993-09-01 |chapter-url=https://dl.acm.org/doi/10.1145/166266.166274 |series=ACM Multimedia |location=New York City |publisher=Association for Computing Machinery |pages=75–82 |doi=10.1145/166266.166274 |isbn=978-0-89791-596-0|s2cid=3773268 }} Reference 3 in the paper is to Committee Draft of Standard ISO/IEC 11172, December 6, 1991.</ref>
| latest_release_version = ISO/IEC 13818-3:1998
| latest_release_date = {{start date and age|1998|04|df=y}}
| type          = [[Lossy compression|Lossy]] [[Audio file format|audio]]
| container for = 
| contained by  = [[Elementary stream|MPEG-ES]]
| extended from = 
| extended to   = 
| standard      = [[ISO/IEC 11172-3]],<ref name="11172-3">{{cite web |url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=22412 |title=ISO/IEC 11172-3:1993 – Information technology — Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s — Part 3: Audio |publisher=ISO |year=1993 |access-date=2010-07-14}}</ref> [[ISO/IEC 13818-3]]<ref name="13818-3">{{cite web |url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=22991 |title=ISO/IEC 13818-3:1995 – Information technology — Generic coding of moving pictures and associated audio information — Part 3: Audio |publisher=ISO |year=1995 |access-date=2010-07-14}}</ref>
| open          = Yes
| free          = Expired patents<ref>{{cite tech report |publisher=Library of Congress |location=Washington, D.C. |series=Sustainability of Digital Formats |type=Partial draft |title=MPEG-1 and MPEG-2 Layer II Audio Encoding |date=17 May 2012 |url=https://www.loc.gov/preservation/digital/formats/fdd/fdd000338.shtml |access-date=1 December 2021}}</ref>
| url           = http://mpeg.chiariglione.org/standards/mpeg-1/audio.html
}}

'''MP2''' (formally '''MPEG-1 Audio Layer II''' or '''MPEG-2 Audio Layer II''', sometimes incorrectly called '''Musicam'''<ref name="mpegfaq">{{cite web |year=1998 |title=MPEG Audio FAQ Version 9 |url=http://mpeg.chiariglione.org/faq/mp1-aud/mp1-aud.htm#16 |access-date=2010-08-22}}</ref>) is a [[lossy data compression|lossy]] [[audio compression format]]. It is standardised as one of the three audio codecs of [[MPEG-1]] alongside [[MPEG-1 Audio Layer I]] (MP1) and [[MPEG-1 Audio Layer III]] (MP3). The MP2 abbreviation is also used as a common [[Filename extension|file extension]] for files containing this type of audio data, or its extended variant MPEG-2 Audio Layer II. 

MPEG-1 Audio Layer II was developed by [[Philips]], [[Centre commun d'études de télévision et télécommunications|CCETT]] and [[Institut für Rundfunktechnik|IRT]] as the MUSICAM algorithm, as part of the European-funded [[Digital Audio Broadcasting]] (DAB) project.<ref>{{Cite web |date=2002-04-06 |title=Audio Coding |url=http://www.public.asu.edu/~rampriya/audiocoding.htm |access-date=2025-04-17 |archive-url=https://web.archive.org/web/20020406172256/http://www.public.asu.edu/~rampriya/audiocoding.htm |archive-date=6 April 2002 }}</ref> Alongside its use on DAB broadcasts, the codec has been adopted as the standard audio format for [[Video CD]] and [[Super Video CD]] media, and also for [[HDV]].<ref>{{cite web |author=Techopedia |date=16 February 2015 |title=MPEG-1 Audio Layer II (MP2) |url=https://www.techopedia.com/definition/964/mpeg-1-audio-layer-ii-mp2 |access-date=2022-03-17 |publisher=techopedia.com}}</ref> On the other hand, MP3 (which was developed by a rival collaboration led by [[Fraunhofer Society]] called ASPEC) gained more widespread acceptance for [[personal computer|PC]] and [[Internet]] applications. MP2 compresses less than MP3, but therefore also has less computational demands.<ref>{{Cite web |title=MPEG-1 Audio Layer II - Glossary |url=https://www.devx.com/terms/mpeg-1-audio-layer-ii/ |access-date=2025-04-17 |website=DevX |language=en-US}}</ref>
==Technical specifications==
MPEG-1 Audio Layer II is defined in ISO/IEC 11172-3 (MPEG-1 Part 3)

*[[Sampling rate]]s: 32, 44.1 and 48&nbsp;kHz
*[[Bit rate]]s: 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 and 384&nbsp;kbit/s

An extension has been provided in MPEG-2 Audio Layer II and is defined in ISO/IEC 13818-3 (MPEG-2 Part 3)<ref name="mpeg-2-layer-1-2">{{cite web | url=http://mpeg.chiariglione.org/technologies/mpeg-2/mp02-aud/index.htm | title=MPEG-2 Audio Layer I/II | author=Werner Oomen, Leon van de Kerkhof | publisher=chiariglione.org | access-date=2009-12-29}}</ref><ref name="mpeg-audio-frame-header">{{cite web |author=Predrag Supurovic |url=https://www.datavoyage.com/mpgscript/mpeghdr.htm |title=MPEG Audio Frame Header |date=September 1998 |access-date=2009-07-11}}</ref>

*Additional sampling rates: 16, 22.05 and 24&nbsp;kHz
*Additional bit rates: 8, 16, 24, 40 and 144&nbsp;kbit/s
*[[MPEG Multichannel|Multichannel support]] - up to 5 full range audio channels and an LFE-channel (Low Frequency Enhancement channel)

The format is based on successive digital frames of 1152 sampling intervals with four possible formats:
* mono format
* stereo format
* intensity encoded joint stereo format (stereo irrelevance)
* dual channel (uncorrelated) format

=== Variable bit rate ===

MPEG audio may have [[variable bit rate]] (VBR), but it is not widely supported. Layer II can use a method called bit rate switching. Each frame may be created with a different bit rate.<ref name="mpeg-audio-frame-header" /><ref>ISO MPEG Audio Subgroup, [http://mpeg.chiariglione.org/faq/mp1-aud/mp1-aud.htm#15 MPEG Audio FAQ Version 9, MPEG-1 and MPEG-2 BC], retrieved on 2009-07-11.</ref>
According to ISO/IEC 11172-3:1993, Section 2.4.2.3: To provide the smallest possible delay and complexity, the (MPEG audio) decoder is not required to support a continuously variable bit rate when in layer I or II.<ref>[http://www.twolame.org/doc/vbr.html TwoLAME: MPEG Audio Layer II VBR], retrieved on 2009-07-11.</ref>

=== MPEG-2 Audio Layer II ===
While the term MP2 and [[filename extension]] <code>.mp2</code> usually refer MPEG-1 Audio Layer II data, it can also refer to MPEG-2 Audio Layer II, a mostly backward compatible extension which adds support for [[Surround sound|multichannel audio]], [[variable bit rate]] encoding, and additional sampling rates, defined in ISO/IEC 13818-3 as part of [[MPEG-2]] standards.

==Technique==
{{See also|MPEG-1#Layer II}}

MP2 is a [[sub-band coding|sub-band audio encoder]], which means that compression takes place in the [[time domain]] with a low-delay filter bank producing 32 frequency domain components. By comparison, [[MP3]] is a [[Audio data compression#Transform domain methods|transform audio encoder]] with hybrid filter bank, which means that compression takes place in the [[frequency domain]] after a hybrid (double) transformation from the time domain. MPEG Audio Layer II is the core algorithm of the MP3 standards. All psychoacoustical characteristics and frame format structures of the MP3 format are derived from the basic MP2 algorithm and format.

The MP2 encoder may exploit inter channel redundancies using optional "joint stereo" [[Joint stereo#Intensity stereo coding|intensity encoding]]. Like MP3, MP2 is a perceptual coding format, which means that it removes information that the human auditory system will not be able to easily perceive. To choose which information to remove, the audio signal is analyzed according to a psychoacoustic model, which takes into account the parameters of the human auditory system. Research into [[psychoacoustics]] has shown that if there is a strong signal on a certain frequency, then weaker signals at frequencies close to the strong signal's frequency cannot be perceived by the human auditory system. This is called frequency masking. Perceptual audio codecs take advantage of this frequency masking by ignoring information at frequencies that are deemed to be imperceptible, thus allowing more data to be allocated to the reproduction of perceptible frequencies.

MP2 splits the input audio signal into 32 sub-bands, and if the audio in a sub-band is deemed to be imperceptible then that sub-band is not transmitted. MP3, on the other hand, transforms the input audio signal to the frequency domain in 576 frequency components. Therefore, MP3 has a higher frequency resolution than MP2, which allows the psychoacoustic model to be applied more selectively than for MP2. So MP3 has greater scope to reduce the bit rate.

The use of an additional [[entropy coding]] tool, and higher frequency accuracy (due to the larger number of frequency sub-bands used by MP3) explains why MP3 does not need as high a bit rate as MP2 to get an acceptable audio quality. Conversely, MP2 shows a better behavior than MP3 in the time domain, due to its lower frequency resolution. This implies less codec time delay&nbsp;— which can make editing audio simpler&nbsp;— as well as "ruggedness" and resistance to errors which may occur during the [[digital recording]] process, or during transmission errors.

The MP2 sub-band filter bank also provides an inherent "[[Transient (acoustics)|transient]] concealment" feature, due to the specific temporal masking effect of its mother filter. This unique characteristic of the MPEG-1 Audio family implies a very good sound quality on audio signals with rapid energy changes, such as percussive sounds. Because both the MP2 and MP3 formats use the same basic sub-band filter bank, both benefit from this characteristic.

==Applications of MP2==

=== Live broadcasts ===
MPEG-1 Audio Layer II is the audio format used in [[Digital Audio Broadcast]] (DAB), a [[digital radio]] [[international standard|standard]] for [[broadcasting]] [[digital audio radio service]]s that has been adopted in many regions around the world. The [[BBC]] Research & Development department states that at least 192&nbsp;kbit/s is necessary for a [[high fidelity]] stereo broadcast:{{blockquote|A value of 256&nbsp;kbit/s has been judged to provide a high quality stereo broadcast signal. However, a small reduction, to 224&nbsp;kbit/s is often adequate, and in some cases it may be possible to accept a further reduction to 192&nbsp;kbit/s, especially if redundancy in the stereo signal is exploited by a process of 'joint stereo' encoding (i.e. some sounds appearing at the centre of the stereo image need not be sent twice). At 192&nbsp;kbit/s, it is relatively easy to hear imperfections in critical audio material.|BBC R&D White Paper WHP 061 June 2003<ref name=":1">{{cite web |url=http://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP061.pdf |title=BBC R&D White Paper WHP 061 June 2003, DAB:An introduction to the EUREKA DAB System and a guide to how it works |publisher=BBC.co.uk |access-date=2007-05-08 |archive-date=2009-03-04 |archive-url=https://web.archive.org/web/20090304001258/http://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP061.pdf |url-status=live }}</ref>}}

As of 2025, MPEG-1 Audio Layer II remains in widespread use in the United Kingdom for DAB broadcasts; the newer DAB+ standard which is now predominant elsewhere in Europe and in other regions does not use MP2 but [[HE-AAC]] instead.<ref>http://www.frequencyfinder.org.uk/Introduction_to_DAB.pdf</ref> MP2 was also adopted as the audio format used by [[Astra Digital Radio]] (ADR) broadcasts and by the [[Multimedia Home Platform]] (DVB-MHP) standard for set-top boxes. MP2 is also used alongside [[Dolby Digital|Dolby Digital (AC3)]] in the audio streams for some [[DVB]] broadcasts.<ref>{{Cite web |title=DVB · carfax |url=https://www.carfax.org.uk/docs/8/ |access-date=2025-04-17 |website=www.carfax.org.uk}}</ref>

MPEG-1 Audio Layer II is commonly used{{Update inline|date=April 2025}} within the broadcast industry for distributing live audio over satellite, ISDN and IP Network connections as well as for storage of audio in digital playout systems. An example is [[NPR]]'s [[Public Radio Satellite System|PRSS]] Content Depot programming distribution system. The Content Depot distributes MPEG-1 L2 audio in a Broadcast Wave File wrapper. MPEG2 with RIFF headers (used in <code>.wav</code>) is specified in the RIFF/WAV standards. As a result, Windows Media Player will directly play Content Depot files, however, less intelligent <code>.wav</code> players often do not. As the encoding and decoding process would have been a significant drain on CPU resources in the first generations of broadcast playout systems, professional broadcast playout systems typically implement the codec in hardware, such as by delegating the task of encoding and decoding to a compatible soundcard rather than the system CPU.

=== Distributed and recordable media ===
MPEG-1 Audio Layer II is the standard audio format used in the [[Video CD]] and [[Super Video CD]] formats (VCD and SVCD also support variable bit rate and [[MPEG Multichannel]] as added by MPEG-2). All [[DVD-Video]] players in [[PAL]] countries contain stereo MP2 decoders, making MP2 a possible competitor to [[Dolby Digital|Dolby Digital (AC3)]] in these markets. DVD-Video players in [[NTSC]] countries are not required to decode MP2 audio, although most do. While some [[DVD recorder]]s store audio in MP2 and many consumer-authored DVDs use the format, commercial DVDs with MP2 soundtracks are rare.

MPEG-1 Audio Layer II is also the audio format used in [[HDV]] camcorders. 

== Encoders and decoders ==
MPEG-1 Audio Layer II (MP2) [[Encoder (digital)|encoder]] software include [[TooLAME]], MP2ENC (Wav2mp), [[QDesign]] Imedia 2, and others.<ref name=":0">{{Cite web |title=Best of Audio Compression Technology |url=https://www.rarewares.org/rrw/mirrors/km/audiocomp1.html |access-date=2025-04-17 |website=www.rarewares.org}}</ref> [[CDex]] and [[Exact Audio Copy]] are some of the [[CD ripping]] software that can encode to MP2.<ref name=":0" /> Many modern [[media player]] software can play MP2 files including [[Winamp]], [[VLC media player|VLC]], [[Windows Media Player]], [[MusicBee]] and [[iTunes]].<ref>{{Cite web |title=.mp2 Extension - List of programs that can open .mp2 files |url=https://extension.nirsoft.net/mp2 |access-date=2025-04-17 |website=extension.nirsoft.net}}</ref>

MP2 files are compatible with some, but not all, [[Digital audio player|digital audio players ("MP3 players")]].
==History of development==
{{See also|MP3#History|MPEG-1#Layer II}}

=== MUSICAM ===
MPEG-1 Audio Layer 2 encoding was derived from the MUSICAM (''Masking pattern adapted Universal Subband Integrated Coding And Multiplexing'') audio codec, developed by [[Centre commun d'études de télévision et télécommunications]] (CCETT), [[Philips]], and the [[Institut für Rundfunktechnik]] (IRT) in 1989 as part of the [[EUREKA 147]] pan-European inter-governmental research and development initiative for the development of a system for the broadcasting of audio and data to fixed, portable or mobile receivers (established in 1987).

It began as the [[Digital Audio Broadcast]] (DAB) project managed by Egon Meier-Engelen of the Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt (later on called Deutsches Zentrum für Luft- und Raumfahrt, German Aerospace Center) in Germany. The European Community financed this project, commonly known as EU-147, from 1987 to 1994 as a part of the [[EUREKA]] research program.

The Eureka 147 System comprised three main elements: MUSICAM Audio Coding (''Masking pattern Universal Sub-band Integrated Coding And Multiplexing''), Transmission Coding & Multiplexing and COFDM Modulation.<ref>{{cite web |author=A J Bower |year=1998 |title=Digital Radio — The Eureka 147 DAB System |url=http://www.bbc.co.uk/rd/pubs/papers/paper_21/paper_21.shtml |access-date=2010-08-22 |publisher=BBC |location=UK}}</ref>

MUSICAM was one of the few codecs able to achieve high audio quality at bit rates in the range of 64 to 192&nbsp;kbit/s per monophonic channel. It has been designed to meet the technical requirements of most applications (in the field of broadcasting, telecommunication and recording on digital storage media) — low delay, low complexity, error robustness, short access units, etc.<ref>{{cite book |last1=Dehery |first1=Y.F. |title=&#91;Proceedings&#93; ICASSP 91: 1991 International Conference on Acoustics, Speech, and Signal Processing |last2=Lever |first2=M. |last3=Urcun |first3=P. |year=1991 |isbn=0-7803-0003-3 |pages=3605–3608 vol.5 |chapter=A MUSICAM source codec for digital audio broadcasting and storage |doi=10.1109/ICASSP.1991.151054 |s2cid=62615197}}</ref><ref name="aes-musicam">{{cite web |year=1991 |title=AES E-Library – Musicam Source Coding |url=http://www.aes.org/e-lib/browse.cfm?elib=5398 |access-date=2010-08-22}}</ref>

As a predecessor of the MP3 format and technology, the perceptual codec MUSICAM is based on integer arithmetics 32 subbands transform, driven by a psychoacoustic model. It was primarily designed for Digital Audio Broadcasting and digital TV, and disclosed by CCETT(France) and IRT (Germany) in Atlanta during an IEEE-ICASSP conference.<ref>{{cite conference |last1=Dehery |first1=Y.F. |last2=Lever |first2=M. |last3=Urcun |first3=P. |date=May 1991 |title=A MUSICAM source codec for Digital Audio Broadcasting and storage |pages=3605–3608 |doi=10.1109/ICASSP.1991.151054 |isbn=0-7803-0003-3 |work=[Proceedings] ICASSP 91: 1991 International Conference on Acoustics, Speech, and Signal Processing}}</ref> This codec incorporated into a broadcasting system using COFDM modulation was demonstrated on air and on the field <ref>{{cite magazine |last=Box |first=Alan |date=1991-04-15 |title=A DAB commentary from Alan Box, EZ communication and chairman NAB DAB task force |url=http://www.americanradiohistory.com/Archive-BC/BC-1991/BC-1991-04-15.pdf |magazine=[[Broadcasting & Cable|Broadcasting]] |pages=26 |volume=150 |number=15}}</ref> together with [[Ici Radio-Canada Télé|Radio Canada]] and [[Communications Research Centre Canada|CRC Canada]] during the NAB show (Las Vegas) in 1991. The implementation of the audio part of this broadcasting system was based on a two chips encoder (one for the subband transform, one for the psychoacoustic model designed by the team of [[G. Stoll]] (IRT Germany), later known as Psychoacoustic model I in the ISO MPEG audio standard) and a real time decoder using one [[Motorola 56001]] [[Digital Signal Processor|DSP]] chip running an integer arithmetics software designed by [[Y.F. Dehery]]'s team ([[Centre commun d'études de télévision et télécommunications|CCETT]], France). The simplicity of the corresponding decoder together with the high audio quality of this codec using for the first time a 48&nbsp;kHz sampling frequency, a 20 bits/sample input format (the highest available sampling standard in 1991, compatible with the AES/EBU professional digital input studio standard) were the main reasons to later adopt the characteristics of MUSICAM as the basic features for an advanced digital music compression codec such as MP3.

The audio coding algorithm used by the Eureka 147 Digital Audio Broadcasting (DAB) system has been subject to the standardization process within the ISO/Moving Pictures Expert Group (MPEG) in 1989–94.<ref name="etsi">{{citation |title=Digital Audio Broadcasting (DAB); DAB to mobile, portable and fixed receivers – Details of 'DE/JTC-DAB' Work Item – ETS 300 401 |date=1995-02-15 |url=http://webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=976 |access-date=2010-08-23}}</ref><ref>{{citation |title=DAB – Service planning for terrestrial Digital Audio Broadcasting |year=1992 |url=http://www.ebu.ch/trev_252-lau.pdf |access-date=2010-08-22 |archive-url=https://web.archive.org/web/20050504183626/http://www.ebu.ch/trev_252-lau.pdf |archive-date=2005-05-04 |url-status=dead}}</ref> MUSICAM audio coding was used as a basis for some coding schemes of MPEG-1 and MPEG-2 Audio.<ref name="santaclara">{{cite web |year=1990 |title=Status report of ISO MPEG – September 1990 |url=http://mpeg.chiariglione.org/meetings/santa_clara90/santa_clara_press.htm |url-status=dead |archive-url=https://web.archive.org/web/20100214044029/http://mpeg.chiariglione.org/meetings/santa_clara90/santa_clara_press.htm |archive-date=2010-02-14 |access-date=2010-08-22}}</ref> Most key features of MPEG-1 Audio were directly inherited from MUSICAM, including the filter bank, time-domain processing, audio frame sizes, etc. However, improvements were made, and the actual MUSICAM algorithm was not used in the final MPEG-1 Audio Layer II standard.

Since the finalisation of MPEG-1 Audio and MPEG-2 Audio (in 1992 and 1994), the original MUSICAM algorithm is not used anymore.<ref name="mpegfaq" /><ref name="telos">{{cite web |author=Telos Systems |title=Facts about MPEG compression |url=http://www.telos-systems.com/techtalk/mpeg/default.htm |url-status=dead |archive-url=https://web.archive.org/web/20010508092243/http://www.telos-systems.com/techtalk/mpeg/default.htm |archive-date=2001-05-08 |access-date=2010-08-22}}</ref> The name MUSICAM is often mistakenly used when MPEG-1 Audio Layer II is meant. This can lead to some confusion, because the name MUSICAM is trademarked by different companies in different regions of the world.<ref name="mpegfaq" /><ref name="telos" /><ref>{{cite web |author=MUSICAM USA |title=MUSICAM USA Frequently Asked Questions – Isn't MUSICAM simply your implementation of ISO/MPEG Layer 2? |url=http://www.musicamusa.com/faq2.htm |access-date=2010-08-23}}</ref> (Musicam is the name used for MP2 in some specifications for Astra Digital Radio as well as in the BBC's DAB documents.)

The Eureka Project 147 resulted in the publication of European Standard, ETS 300 401 in 1995, for DAB which now has worldwide acceptance. The DAB standard uses the MPEG-1 Audio Layer II (ISO/IEC 11172-3) for 48&nbsp;kHz sampling frequency and the MPEG-2 Audio Layer II (ISO/IEC 13818-3) for 24&nbsp;kHz sampling frequency.<ref>{{citation |title=Radio Broadcasting Systems; Digital Audio Broadcasting (DAB) to mobile, portable and fixed receivers – Details of 'REN/JTC-DAB-36' Work Item – EN 300 401 |date=2006-06-15 |url=http://webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=21095 |access-date=2010-08-23}}</ref>

=== MPEG Audio ===
In the late 1980s, [[International Organization for Standardization|ISO]]'s [[Moving Picture Experts Group]] (MPEG) started an effort to standardize digital audio and video encoding, expected to have a wide range of applications in digital radio and TV broadcasting (later [[Digital audio broadcasting|DAB]], [[Digital Multimedia Broadcasting|DMB]], [[Digital video broadcasting|DVB]]), and use on CD-ROM (later [[Video CD]]).<ref>{{cite web |last=Chiariglione |first=Leonardo |date=October 1989 |title=MPEG Press Release |url=http://mpeg.chiariglione.org/meetings/kurihama89/kurihama_press.htm |archive-url=https://web.archive.org/web/20100805102339/http://mpeg.chiariglione.org/meetings/kurihama89/kurihama_press.htm |archive-date=2010-08-05 |publisher=[[Moving Picture Experts Group]] |location=Kurihama}}.</ref> The MUSICAM audio coding was one of 14 proposals for MPEG-1 Audio standard that were submitted to ISO in 1989.<ref name="aes-musicam" /><ref name="santaclara" />

The MPEG-1 Audio standard was based on the existing MUSICAM and ASPEC audio formats.<ref>Digital Video and Audio Broadcasting Technology: A Practical Engineering Guide (Signals and Communication Technology) {{ISBN|3-540-76357-0}} p. 144: "In the year 1988, the MASCAM method was developed at the Institut für Rundfunktechnik (IRT) in Munich in preparation for the digital audio broadcasting (DAB) system. From MASCAM, the MUSICAM (masking pattern universal subband integrated coding and multiplexing) method was developed in 1989 in cooperation with CCETT, Philips and Matsushita."</ref>
The [[MPEG-1]] Audio standard included the three audio "layers" (encoding techniques) now known as Layer I (MP1), Layer II (MP2) and Layer III (MP3).
All algorithms for MPEG-1 Audio Layer I, II and III were approved in 1991 as the committee draft of ISO-11172<ref name="cd-1991">{{cite web |last=Chiariglione |first=Leonardo |date=November 1991 |title=MPEG Press Release |url=http://mpeg.chiariglione.org/meetings/kurihama91/kurihama_press.htm |url-status=dead |archive-url=https://web.archive.org/web/20110503174827/http://mpeg.chiariglione.org/meetings/kurihama91/kurihama_press.htm |archive-date=2011-05-03 |access-date=2010-07-17 |publisher=[[Moving Picture Experts Group]] |location=Kurihama}}</ref><ref name="neuron2-cd-1991">{{cite web |author=ISO |date=November 1991 |title=CD 11172-3 - Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to About 1.5 MBit/s Part 3 Audio |url=http://neuron2.net/library/mpeg1/MPGAUDIO.DOC |archive-url=https://web.archive.org/web/20100611215029/http://neuron2.net/library/mpeg1/MPGAUDIO.DOC |archive-date=June 11, 2010 |access-date=2010-07-17 |publisher=neuron2.net |format=DOC}}</ref><ref>{{cite conference |last1=Patel |first1=Ketan |last2=Smith |first2=Brian C. |last3=Rowe |first3=Lawrence A. |title=Performance of a Software MPEG Video Decoder |url=http://www.cs.unc.edu/~kmp/publications/mm93/MM93-paper.pdf |conference=ACM Multimedia 1993 Conference}} Article's reference 3 is: 'ISO/IEC JTC/SC29, "Coded Representation of Picture, Audio and Multimedia/Hypermedia Information", ''Committee Draft of Standard ISO/IEC 11172'', December 6, 1991'.</ref> and finalized in 1992<ref name="dis-1992">{{cite web |author=ISO |date=1992-11-06 |title=MPEG Press Release, London, 6 November 1992 |url=http://mpeg.chiariglione.org/meetings/london/london_press.htm |url-status=dead |archive-url=https://web.archive.org/web/20100812034709/http://mpeg.chiariglione.org/meetings/london/london_press.htm |archive-date=12 August 2010 |access-date=2010-07-17 |website=Chiariglione.org}}</ref> as part of [[MPEG-1]], the first standard suite by [[MPEG]], which resulted in the international standard '''[[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] 11172-3''' (a.k.a. ''MPEG-1 Audio'' or ''MPEG-1 Part 3''), published in 1993.<ref name="11172-3" /> Further work on MPEG audio<ref name="sydney1993">{{cite press release |title=Press Release - Adopted at 22nd WG11 meeting |date=1993-04-02 |publisher=[[International Organization for Standardization]] |url=http://mpeg.chiariglione.org/meetings/sydney93/sydney_press.htm |access-date=2010-07-18 |url-status=dead |archive-url=https://web.archive.org/web/20100806161942/http://mpeg.chiariglione.org/meetings/sydney93/sydney_press.htm |archive-date=2010-08-06}}</ref> was finalized in 1994 as part of the second suite of MPEG standards, [[MPEG-2]], more formally known as international standard '''ISO/IEC 13818-3''' (a.k.a. ''MPEG-2 Part 3'' or [[backward compatible]] ''MPEG-2 Audio'' or ''MPEG-2 Audio BC''<ref name="mpeg-audio-faq-bc">{{cite web |author=ISO |date=October 1998 |title=MPEG Audio FAQ Version 9 - MPEG-1 and MPEG-2 BC |url=http://mpeg.chiariglione.org/faq/mp1-aud/mp1-aud.htm |access-date=2009-10-28 |publisher=ISO}}</ref>), originally published in 1995.<ref name="13818-3" /><ref name="Brandenburg1997">{{cite journal |last1=Brandenburg |first1=Karlheinz |last2=Bosi |first2=Marina |date=February 1997 |title=Overview of MPEG Audio: Current and Future Standards for Low-Bit-Rate Audio Coding |url=http://www.aes.org/e-lib/browse.cfm?elib=7871 |journal=Journal of the Audio Engineering Society |volume=45 |issue=1/2 |pages=4–21 |access-date=30 June 2008}}</ref> MPEG-2 Part 3 (ISO/IEC 13818-3) defined additional bit rates and sample rates for MPEG-1 Audio Layer I, II and III. The new sampling rates are exactly half that of those originally defined for MPEG-1 Audio. MPEG-2 Part 3 also enhanced MPEG-1's audio by allowing the coding of audio programs with more than two channels, up to 5.1 multichannel.<ref name="sydney1993" />

The Layer III ([[MP3]]) component uses a [[lossy compression]] algorithm that was designed to greatly reduce the amount of data required to represent an audio recording and sound like a decent reproduction of the original uncompressed audio for most listeners.

===Emmy Award in Engineering===
[[Centre commun d'études de télévision et télécommunications|CCETT]] (France), [[Institut für Rundfunktechnik|IRT]] (Germany) and [[Philips]] (The Netherlands) won an [[Emmy Award]] in Engineering 2000 for development of a digital audio two-channel compression system known as Musicam or MPEG Audio Layer II.<ref>{{citation |title=National Academey of Television Arts and Sciences, Outstanding Achievement in Technical/Engineering Development Awards |url=http://www.emmyonline.tv/tech/applications/engineering_award_winners_rev3.pdf |access-date=2010-08-01 |archive-url=https://web.archive.org/web/20100414233617/http://www.emmyonline.tv/tech/applications/engineering_award_winners_rev3.pdf |archive-date=2010-04-14 |url-status=dead}}</ref><ref>{{cite web |date=2001-02-11 |title=CCETT - DAB : Digital Audio Broadcasting (archived website) |url=http://www.ccett.fr/eng/03b2.htm |archive-url=https://web.archive.org/web/20010211120613/http://www.ccett.fr/eng/03b2.htm |archive-date=2001-02-11 |access-date=2010-08-01}}</ref>

==See also==
* [[MPEG-1]]
** [[MPEG-1 Audio Layer I]]
** [[MP3|MPEG-1 Audio Layer III]]
* [[MPEG-2]]
* [[MPEG-4 Part 14|MP4 (container format)]]
* [[Elementary stream]]
* [[Musepack]] originally MP2-based, with numerous improvements

==Notes==
{{Reflist|30em}}

==References==
{{Refbegin}}
* [http://www.tnt.uni-hannover.de/~musmann/index.php Genesis of the MP3 Audio Coding Standard by Hans Georg Musmann ] in IEEE Transactions on Consumer Electronics, Vol. 52, Nr. 3, pp.&nbsp;1043–1049, August 2006
* MUSICAM Source Coding by Yves-François Dehery, AES 10th International Conference: Kensington, London, England, (7-9 Sept 1991), pp 71–79.
{{Refend}}

==External links==
* [http://www.iis.fraunhofer.de/en/bf/amm/mp3history.html The history of MP3 from Fraunhofer IIS]
* [https://web.archive.org/web/20021214015841/http://www.mpeg.org/MPEG/audio.html MPEG Audio Resources and Software]
* [http://toolame.sourceforge.net/ TooLAME] – An MP2 encoder
* [http://www.twolame.org/ TwoLAME] – A fork of the tooLAME code
* {{IETF RFC|3003}} – The document defining MIME type for MPEG-1 Audio Layer II
* [https://web.archive.org/web/20090214074004/http://keyj.s2000.ws/?p=50 A MPEG Audio Layer II decoder in 4k] – Source code for small open source decoder.
* [http://mpeg.chiariglione.org/ Official MPEG web site]
* [https://web.archive.org/web/20080916215441/http://www.kuro5hin.org/story/2008/7/18/232618/312 Patent Status of MPEG-1, H.261 and MPEG-2] – Some information about patents

{{Audio broadcasting}}
{{Compression formats}}
{{MPEG}}

[[Category:Audio codecs]]
[[Category:MP3]]
[[Category:MPEG]]